According to tradition, Israel was a small tribe under the Patriarchs. We lost our freedom in Egypt, sprouted a new nation under Moses and Joshua, and continued as such until the end of Solomon's reign. Two Jewish states, Israel and Judea, emerged side by side. Israel was lost, and Judea ended up in Babylonian captivity.
The term "Sadducees" comes from the name of Zadok, the first High Priest of Solomon's Temple (950 BCE-ish). Sadducees practiced the religion of Hebraism. Hebraism accepts only the Five Books of Moses; it discards the Prophetic texts and the Rabbinic texts, including the Talmud. The Hebrews didn't believe in resurrection, an afterlife, or a messiah. They did believe in a cult god who punishes in this lifetime, but this is not the universal God of Judaism. The Sadducees didn't believe in direct prayer to God, but in the intercession of the priesthood through animal and grain sacrifices.
And so, when the Temple was destroyed in 586 BCE, and the two remaining tribes, Judah and Benjamin, were captured and taken to Babylon, they could no longer worship as Hebrews. Rabbinic Judaism emerged from this group. While some of our people stayed in the Persian empire, others returned to Judea, where they lived under Greek rule and later Roman authority, with a short-lived period of independence in between, following the Bar Kochba rebellion.
During the first generation of religious teachers known as the Zugot (515 BCE - 70 CE), supporters of Hellenism gained control over the position of the High Priest, the Kohen HaGadol. Greek sympathizers were appointed to fill that role. The people elected a nasi, a chief of the courts, as an alternative to the corrupt Temple priests. Thus began a rift between the Sadducees and the Pharisees (separatists who were the forerunners of modern Rabbinic Judaism). Pairs of Zugot led the Sanhedrin. One was the Nasi, and the other was called the Av Beit Din (literally "father of the court") whose role was to oversee the judges. Following the Hashmonian-Maccabean revolt (around 165 BCE), religious authority shifted from the priests to the courts. After the destruction of the Second Temple in 70 CE, the Beit Din HaGadol, the High Court, ceased to exist. The Romans allowed the Sanhedrin to be re-established at Jamnia, but as the influence of Christianity grew, the Romans shut down the Sanhedrin in order to marginalize Judaism. Hillel (traditionally said to have lived from 110 BCE to 10 CE) and Shammai (b 50 BCE, d 30 CE) were the last pair of leaders of the Zugot period, and served at the time of King Herod (who lived from around 74 BCE to 4 BCE).
The era of the Tannaim, 10-220 CE, began with the emergence of the House of Hillel and the House of Shammai, two schools of thought with very different perspectives on Jewish law. Disagreements between them appear throughout the Talmud. According to tradition, the Tannaim were the final transmitters of the Oral Law, which had been passed from teacher to student from the time of Moses. The Tannaim include approximately 120 sages whose views are recorded in the Mishna. The root tanna corresponds to the Aramaic word for the Hebrew shanah, which is also the root word for Mishna, meaning to repeat, or to teach. The Tannaim lived and taught from the time of the Roman occupation of Judea, through the destruction of the Second Temple, and the periods before and after the Bar Kokhba rebellion. Among them are Rabban Yohanan ben Zakki (40 BCE - 80 CE), Rabban Gamliel of Yavneh, Rabbi Eliezer, Rabbi Yehoshua, Rabbi Akiva, Rabbi Meir, Rabbi Yehuda, and Rabbi Judah HaNasi.
The Amoraim (200 CE - 500 CE) taught the Oral Law in Babylonia and Israel, and their debates were codified in the Gemara. 761 Amoraim are mentioned in both Talmuds (Bavli and Yerushalmi). 367 lived in Israel from around 200-350 CE, and the other 394 lived in Babylon from around 200-500 CE. Amoraim is an Aramaic word that means "those who say."
Savora, which means "reasoner," is a term used in Jewish law and history to signify the rabbis who are credited with having given the Talmud much of its current structure, i.e. the editors. They did this work from approximately 500 CE - 700 CE. Modern scholars also use the plural stammaim for authors of unattributed statements in the Gemara. Classical rabbinic literature holds that the Babylonian Talmud was redacted into its final form circa 550 CE. Some statements within classical rabbinic literature and later analysis have led some to conclude that the Bavli was smoothed over by the Savora'im, although little was altered.
The Geonim, from 589 CE to 1038 CE, preserved the transmission of Torah and halakhah, Jewish law. They taught the Talmud, and made legal decisions on issues for which no prior ruling existed. Geonim is the plural of Gaon, which means "pride" or "splendor" in Biblical Hebrew, and "genius" in modern Hebrew. These rabbis of the medieval period led the Talmudic academies of Sura and Pumbedita in the Abbasid Caliphate. Their schools were the center of Jewish learning, and they were consulted from abroad on matters of Jewish law. Their questions and answers were compiled to form what is known as the Responsa literature. Later Geonim consulted not only the Mishna and Talmud, but also the decisions made by their predecessors, whose opinions were generally regarded as authoritative. By the 10th century, as learning spread to other regions, Jewish communities consulted experts in their own countries.
The Rishonim lived in the 11th - 15th centuries. Rishon means "the first ones" and refers to rabbis who lived prior to the publication of the Shulkhan Aruch of Yosef Karo in 1563. The publication of the Shulkhan Aruch marks the transition from the era of Rishonim to that of the Acharonim, or "last ones" (from the 16th century to the present.) According to Orthodox Jewish tradition, the Acharonim cannot dispute the rulings of rabbis of previous eras unless they find support from other rabbis of previous eras. The question of which prior rulings can or cannot be disputed has resulted in a need to determine exactly which rulings fall within this period. Some rabbis hold that Yosef Karo's Beit Yosef has the halakhic status of a work of a Rishon, while the later Shulkhan Aruch has the status of a work of an Acharon.